GGT6 and hepatocellular carcinoma: DNA methylation of GGT1 (P = 0.0067, Figure 5A), GGT5 (P < 0.0001, Figure 5B), and GGT7 (P = 0.046, Figure 5C) was significantly higher in normal tissues than in the corresponding HCC specimens, with the exception of GGT6 (P = 0.09, Figure 5D).